Internal gear pumps and motors

ABSTRACT

The invention relates to internal gear pumps and motors having a pinion meshed with an internal gear and rotatable in a housing, and in which a crescent-shaped member is disposed between the pinion and the internal gear where these are not interengaged. According to the invention a pair of sideplates are arranged to press against opposite axial end faces of the piston and internal gear, one of the plates being fixed and the other movable by hydraulic pressure. The crescent-shaped member is secured relative to the fixed sideplate and is slidable in the other sideplate. A pair of apertures in each sideplate communicate respectively with high- and low-pressure ports in the housing. A sealing element between the crescent-shaped member and the movable sideplate extends over at least that portion of the crescent-shaped member which is adjacent to the aperture connected to the high-pressure port. The sideplates may each be formed with a pair of grooves which extend around opposite sides of the crescent-shaped member from the aperture connected to the low-pressure port. Where such grooves are present the sealing element extends only as far as the ends of grooves, since fluid in these is at low pressure. The sealing element is conveniently carried in a recess in the crescent-shaped member. A sealing element may also be fitted between the crescent-shaped member and the sideplate.

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eplate and is slidable in the other side tures in each sideplate communicate re and low-pressure ports in the housin between the crescent-shaped memb sideplate extends over at least that shaped member which is adjacent t to the high-pressure port. The side with a pair of grooves which exte the crescent-shaped member from the a conveniently carried in a recess in the cre member. A sealing element may also be fitted between crescent-shaped member and the sideplate.

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3,270,679 9/1966 Sandetal..................... 103/126A Patented Aug. 3, 1971 3,597,129

5 Sheets-Sheet 1 IN ENTOR 4%44/ 400% ATTS NEYS 5 Sheets-Sheet 2 Patented Aug. 3, 1971 IN\/ NTQE BY W J 4 M ATTORNEYS Patented Aug. 3, 1971 3,597,129

5 Sheets-Sheet L BYDW 'M Patented Aug. 3, 1971 5 Sheets-Sheet 5 FIGS g M? Q INTERNAL GEAR PUMPS AND MOTORS This invention relates to internal gear pumps and motors of the kind comprising a housing, an internal gear mounted for rotation within the housing, a pinion mounted within the housing for rotation about an axis parallel to and spaced from the ring gear axis, the teeth of said pinion being meshed with the teeth of said internal gear, a crescent-shaped member within the housing and disposed between the pinion and the internal gear where these are not interengaged and ports formed in the housing at opposite sides of the zone over which the pinion and the ring gear are interengaged.

In pumps and motors of this kind it is required to ensure that leakage of liquid over the axial end faces of the pinion and the internal gear is minimized, but this is made difiicult by the presence of the crescent-shaped member. The present invention sets out to provide an arrangement whereby such leakage is minimized in a convenient manner.

In accordance with the invention in a pump or motor of the kind specified the housing incorporates a pair of sideplates respectively arranged to press against opposite axial end faces of the pinion and the internal gear, one of said sideplates being fixed and the other being movable by hydraulic pressure, the crescent-shaped member being secured relative to the fixed sideplate and being slidably engaged with a part of the movable sideplate, and a sealing element is interposed between the crescent-shaped member and the coacting part of the movable sideplate and extending along the external and internal profiles of the crescent-shaped member at least over a portion thereof adjacent the one of said ports at which high hydraulic pressure is present in use.

Ari example of the invention is shown in the accompanying drawings in which FIG. 1 is a compound cross section through a pump in ac cordance with the invention;

FIGS. 2 to 5 are sections taken respectively on lines A-A, B-B, C-C and D-D in FIG. 1;

FIG. 6 is an enlarged view of the contents of circle E in FIG. 5; and

FIG. 7 is a fragmentary view similar to FIG. I but showing a modified form of the invention.

As shown in the drawings the pump includes a housing 10 in three parts namely end parts 11 and 12 providing bearings 13 for a hollow shaft 14 and an annular intermediate part 15. The axis of the annular intermediate part 15 is spaced from and parallel to the axis of the shaft 14 which has a pinion 16 integrally formed therewith. This pinion 16 has its teeth meshed with the teeth ofan internal gear 17 which runs in a bearing 18 within the annular part 15.

The housing part 12 has secured to it a fixed sideplate 19 which has a planar face against which the axial end faces of the pinion l6 and the gear 17 bear. The opposite axial end faces of the pinion 16 and the gear 17 bear against a movable sideplate 20 fixed to a bell 21 slidable in a cylindrically walled chamber 22 in the part 11. The bell 21 is acted upon by three hydraulic pistons 23, 24 and 25 slidable in bores in the part 1 1. The piston 23 is shown in FIG. 5 from which it will be seen that it acts upon a finger 26 integral with the bell 21.

Secured to the part 12 is a fixed crescent-shaped member 27 which is disposed between the pinion l6 and the gear 17 where these are not interengaged. The internal profile of the member 27 is an arc struck from the axis of the shaft 14 and of radius equal to the external radius of the pinion 16 so that the crests of the teeth thereof wipe this internal surface as the pinion 16 rotates. Similarly the external profile of member 27 is wiped by the crests of the teeth of the gear 17. The housing is formed with a low-pressure inlet port 28 and a high-pressure outlet port 29 both of which are bifurcated and communicate respectively with apertures 30, 31 in the side plates 19, 20. There are passages in the part 11 through which high pressure liquid is applied to the pistons 23, 24, 25, to urge the sideplate 20 into engagement with the gear 17 and the pinion 16. These apertures 30, 31 are disposed respectively on opposite sides of the zone in which the pinion 16 and the gear 17 are interengaged. The plates 19, 20 are formed with grooves 32, 33 extending from the apertures 30 on opposite sides of the crescent-shaped member 27 respectively. These grooves serve, as explained in our British Pat. No. 1,035,529, to prevent cavitation caused by centrifugal action, by continuously allowing liquid to enter the spaces between the teeth of the pinion and the gear at the radially inner extreme of such spaces. The grooves terminate at a position spaced from that end of the crescent-shaped member 27 which is adjacent the high-pressure port, by a distance in excess of the distance between the tooth crests of the pinion l6 and the internal gear 17.

The movable sideplate 20 has a crescent-shaped hole through which the member 27 is a close liding fit. The member 27 is likewise closely fitted into a hole in the plate 19 but in this case there is no requirement for sliding. To prevent leakage of high pressure liquid between the plate 20 and the member 27 the latter is formed in its internal and external profiles with a groove extending around the end of member 27 adjacent the high pressure port and this groove is fitted with a resilient sealing element 34 which engages the coacting face of the plate 20. This sealing element only extends as far as the ends of the grooves 32, 33, since beyond this point the liquid is at low pressure and sealing difficulties do not arise.

The sealing element 34 extends only around a short end portion of the member 27, since as explained above, the grooves 32, 33 maintain low liquid pressure up to this point. If however, the ports are so designed that the grooves 32, 33 are not employed the sealing element 34 will be required to extend around the entire periphery of the member 27, as shown in FIG. 7. In addition it may be convenient, for reasons of ease of manufacture, to employ two sealing elements 34, one being engaged in the hole in the plate 20 and the other being engaged in the hole in the fixed plate 19. The length of the sealing elements will depend upon the design of the low-pressure port.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. An internal gear pump or motor comprising a housing and internal gear mounted for rotation within the housing, a pinion mounted within the housing for rotation about an axis parallel to, and spaced from, the ring gear axis, the teeth of said pinion being meshed with the teeth of said internal gear, a crescent-shaped member within the housing disposed between the pinion and the internal gear where these are not interengaged, ports formed in the housing at opposite sides of a zone over which the pinion and ring gear are interengaged a pair of sideplates in the housing respectively arranged to press against opposite axial end faces of the pinion and internal gear, one of such sideplates being fixed and the other being moveable by hydraulic pressure, the crescent-shaped member being secured relative to the fixed sideplate, and being slidedly engaged in a crescent-shaped hole in the moveable sideplate, and a sealing element interposed between the crescent-shaped member and the internal surface of the hole in the moveable sideplate and extending along the external and internal profiles of the crescent-shaped member at least over a portion thereof adjacent the one of said ports at which high hydraulic pressure is present in use.

2. A pump or motor as claimed in claim 1 in which the said sealing element is carried in a groove in the crescent-shaped member.

3. A pump or motor as claimed in claim 1, in which a sealing element is interposed between the crescent-shaped member and the coacting part of the fixed sideplate.

4. A pump or motor as claimed in claim I in which each said sideplate is formed with a pair of apertures which connect respectively with the highand low-pressure ports of the pump or motor.

5. A pump or motor as claimed in claim 4 in which each said sideplate is formed with a pair of grooves opening onto the 3 ,5 97 1 29 3 4 aperture associated with the low-pressure port and extending crescent-shaped member. either side of the crescent-shaped member. 7. A pump or motor as claimed in claim 5 in which the seal- 6. A pump or motor as claimed in claim 4 in which the sealing element extends only as far as the ends of the said grooves ing element extends around the entire periphery of the remote from the low-pressure port. 

1. An internal gear pump or motor comprising a housing and internal gear mounted for rotation within the housing, a pinion mounted within the housing for rotation about an axis parallel to, and spaced from, the ring gear axis, the teeth of said pinion being meshed with the teeth of said internal gear, a crescentshaped member within the housing disposed between the pinion and the internal gear where these are not interengaged, ports formed in the housing at opposite sides of a zone over which the pinion and ring gear are interengaged a pair of sideplates in the housing respectively arranged to press against opposite axial end faces of the pinion and internal gear, one of such sideplates being fixed and the other being moveable by hydraulic pressure, the crescent-shaped member being secured relative to the fixed sideplate, and being slidedly engaged in a crescent-shaped hole in the moveable sideplate, and a sealing element interposed between the crescent-shaped member and the internal surface of the hole in the moveable sideplate and extending along the external and internal profiles of the crescent-shaped member at least over a portion thereof adjacent the one of said ports at which high hydraulic pressure is present in use.
 2. A pump or motor as claimed in claim 1 in which the said sealing element is carried in a groove in the crescent-shaped member.
 3. A pump or motor as claimed in claim 1, in which a sealing element is interposed between the crescent-shaped member and the coacting part of the fixed sideplate.
 4. A pump or motor as claimed in claim 1 in which each said sideplate is formed with a pair of apertures which connect respectively with the high- and low-pressure ports of the pump or motor.
 5. A pump or motor as claimed in claim 4 in which each said sideplate is formed with a pair of grooves opening onto the aperture associated with the low-pressure port and extending either side of the crescent-shaped member.
 6. A pump or motor as claimed in claim 4 in which the sealing element extends around the entire periphery of the crescent-shaped member.
 7. A pump or motor as claimed in claim 5 in which the sealing element extends only as far as the ends of the said grooves remote from the low-pressure port. 